Electrodes for energy storage devices

ABSTRACT

Disclosed herein is an energy storage cell comprising a first electrode; a second electrode; a permeable separator disposed between the first electrode and the second electrode; and an electrolyte wetting the first and second electrodes; wherein the first electrode comprises a network of dements defining void spaces within the network; and active material comprising lithium metal oxide disposed in the void spaces within the network and enmeshed in the network; wherein the electrode active layer contains less than 0.1% percent by weight of polymeric binders disposed in the void spaces; and wherein the active layer is greater than 99% by weight active material.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationhaving Ser. No. 17/948,644 filed on Sep. 20, 2022, which is acontinuation of U.S. patent application having Ser. No. 17/316,037 filedon May 5, 2021, which is a continuation of U.S. patent applicationhaving Ser. No. 17/114,153 filed on Dec. 7, 2020, now U.S. patent Ser.No. 11/557,765, granted Jan. 17, 2023 and claims the benefit of andpriority to PCT Application having Application No. PCT/US 2020/040943filed on Jul. 6, 2020, which claims the benefits of and priority to eachof U.S. Provisional Pat. App. Ser. No. 63/041,801 filed Jun. 19, 2020;U.S. Provisional Pat. App. Ser. No. 63/003,341 filed Apr. 1, 2020; U.S.Provisional Pat. App. Ser. No. 62/954,771 filed Dec. 30, 2019; U.S.Provisional Pat. App. Ser. No. 62/876,124 filed Jul. 19, 2019; and U.S.Provisional Pat. App. Ser. No. 62/871,041 filed Jul. 5, 2019. The entirecontents of each of the foregoing references are incorporated herein byreference.

BACKGROUND

Lithium batteries are used in many products including medical devices,electric cars, airplanes, and consumer products such as laptopcomputers, cell phones, and cameras. Due to their high energy densities,high operating voltages, and low-self discharges, lithium ion batterieshave overtaken the secondary battery market and continue to find newuses in products and developing industries.

Generally, lithium ion batteries (“LIBs” or “LiBs”) comprise an anode, acathode, and an electrolyte material such as an organic solventcontaining a lithium salt. More specifically, the anode and cathode(collectively, “electrodes”) are formed by mixing either an anode activematerial or a cathode active material with a binder and a solvent toform a paste or slurry which is then coated and dried on a currentcollector, such as aluminum or copper, to form a film on the currentcollector. The anodes and cathodes are then layered or coiled prior tobeing housed in a pressurized casing containing an electrolyte material,which all together forms a lithium ion battery.

In conventional electrodes binder is used with sufficient adhesive andchemical properties such that the film coated on the current collectorwill maintain contact with the current collector even when manipulatedto fit into the pressurized battery casing. Since the film contains theelectrode active material, there will likely be significant interferencewith the electrochemical properties of the battery if the film does notmaintain sufficient contact with the current collector. Further, it hasbeen important to select a binder that is mechanically compatible withthe electrode active material(s) such that it is capable of withstandingthe degree of expansion and contraction of the electrode activematerial(s) during charging and discharging of the battery.

Accordingly, binders such as cellulosic binder or cross-linked polymericbinders have been used to provide good mechanical properties. However,such binder materials have disadvantageous effects. For example, thebulk of the binder fills volume in the electrode active layer whichotherwise could be used to increase the mass loading of active materialand decrease the electrical conductivity of the electrode. Moreover,binders tend to react electrochemically with the electrolyte used in thecell (especially in high voltage, high current, and/or high temperatureapplications), resulting in degradation of the performance of the cell.

SUMMARY

The applicants have realized that an electrode may be constructed toexhibit excellent mechanical stability without the need for bulk polymerbinders. In one aspect, the present disclosure describes embodiments ofan electrode active layer that includes a network of high aspect ratiocarbon elements (e.g., carbon nanotubes, carbon nanotube bundles,graphene flakes, or the like) that provides a highly electricallyconductive scaffold that entangles or enmeshes the active material,thereby supporting the layer. As detailed below, a surface treatment canbe applied to the high aspect ratio carbon elements to promote adhesionto the active material and any underlying electrode layers (e.g., acurrent collector layer) improving the overall cohesion and mechanicalstability of the active layer. This surface treatment forms only a thin(in some cases even monomolecular) layer on the network, leaving thelarge void spaces that are free of any bulk binder material and so mayinstead be filled with active material. The resulting active layer maybe formed with excellent mechanical stability even at large thicknessand high active material mass loading.

In another aspect, the present disclosure describes a method includingdispersing high aspect ratio carbon elements and a surface treatmentmaterial in a solvent to form an initial slurry, wherein said dispersionstep results in the formation of a surface treatment on the high aspectratio carbon; mixing active materials into the first slurry to form afinal slurry; coating the final slurry onto a substrate; and drying thefinal slurry to form an electrode active layer.

Various embodiments may include any of the features or elementsdescribed herein, individually or in any suitable combination.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of an electrode featuring an active materiallayer.

FIG. 2 is a detailed illustration of an embodiment of an active materiallayer.

FIG. 3 is a detailed illustration of another embodiment active materiallayer.

FIG. 4 is an electron micrograph of an active material of the typedescribed herein.

FIG. 5 is a schematic of an energy storage cell.

FIG. 6 is a flow chart illustrating a method of making the electrode ofFIG. 1 .

FIG. 7 shows a schematic of a pouch cell battery

FIG. 8 shows a summary of functional parameters for a pouch cell batteryfor EV applications.

FIG. 9 shows a summary of functional parameters for a pouch cellbattery.

FIG. 10 shows the results of a comparative performance evaluation of apouch cell battery featuring a binder free cathode (left plot) and apouch cell battery featuring a binder based cathode (right plot).

FIG. 11 shows the results of a comparative performance evaluation of apouch cell battery featuring a binder free cathode (upper trace) and apouch cell battery featuring a binder based cathode (lower trace).

FIG. 12 is a schematic of a half cell lithium battery apparatus.

FIG. 13 is a plot showing potential (referenced to the Li/Li+ potential)vs specific capacity for binder free cathode half cell (solid traces)and reference binder based cathode half cell (dashed traces) at variouscurrent densities

FIG. 14 is a plot showing potential (referenced to the Li/Li+ potential)vs volumetric capacity for binder free cathode have cell (solid traces)and reference binder based cathode half cell (dashed traces) at variouscurrent densities

FIG. 15 shows a plot of volumetric capacity vs current density forbinder free cathode half cells (upper trace) and reference binder basedcathode half cell (lower trace).

FIG. 16 shows a Nyquist plot resulting from electrochemical impedancespectroscopy for several binder free cathode half cells (square, circleand triangle labeled traces) and a reference binder based cathode halfcells. The binder free cathode half cells exhibit significantly betterperformance than the reference cell.

DETAILED DESCRIPTION

Referring to FIG. 1 , an electrode 10 is shown which includes an activelayer 100 disposed on a current collector 101. Some embodiment mayinclude an optional adhesion layer 102 disposed between the active layer101 and the current collector 102. In other embodiments, the adhesionlayer 102 may be omitted.

The current collector 101 may be an electrically conductive layer, suchas a metal foil. The optional adhesion layer 102 (which may be omittedin some embodiments) may be a layer of material that promotes adhesionbetween the current collector 102 and the active layer 100. Examples ofsuitable materials for the current collector 101 and the optionaladhesion layer 102 are described in International Patent Publication No.WO/2018/102652 published Jun. 7, 2018.

Electrode Active Layer

In some embodiments, the active layer 100 may include athree-dimensional network 200 of high aspect ratio carbon elements 201defining void spaces within the network 200. A plurality of activematerial particles 300 are disposed in the void spaces within thenetwork 200. Accordingly, the active material particles are enmeshed orentangled in the network 200, thereby improving the cohesion of theactive layer 100.

In some embodiments, a surface treatment 202 (not shown, refer to FIG. 2) is applied on the surface of the high aspect ratio carbon elements 201of the network 200. The surface treatment promotes adhesion between thehigh aspect ratio carbon elements and the active material particles 300.The surface treatment may also promote adhesion between the high aspectratio carbon elements and the current collector 100 (also referred toherein as a “conductive layer”) and/or the option adhesion layer 102.

As used herein, the term “high aspect ratio carbon elements” refers tocarbonaceous elements having a size in one or more dimensions (the“major dimension(s)”) significantly larger than the size of the elementin a transverse dimension (the “minor dimension”).

For example, in some embodiments the high aspect ratio carbon elements201 may include flake or plate shaped elements having two majordimensions and one minor dimension. For example, in some suchembodiments, the ratio of the length of each of the major dimensions maybe at least 5 times, 10 times, 100 times, 500 times, 1,000 times, 5,000times, 10,000 times or more of that of the minor dimension. Exemplaryelements of this type include graphene sheets or flakes.

For example, in some embodiments the high aspect ratio carbon elements201 may include elongated rod or fiber shaped elements having one majordimension and two minor dimensions. For example, in some suchembodiments, the ratio of the length of the major dimensions may be atleast 5 times, 10 times, 100 times, 500 times, 1,000 times, 5,000 times,10,000 times or more of that of each of the minor dimensions. Exemplaryelements of this type include carbon nanotubes, bundles of carbonnanotubes, carbon nanorods, and carbon fibers.

In some embodiments, the high aspect ratio carbon elements 201 mayinclude single wall nanotubes (SWNT), double wall nanotubes (DWNT), ormultiwall nanotubes (MWNT), carbon nanorods, carbon fibers or mixturesthereof. In some embodiments, the high aspect ratio carbon elements 201may be formed of interconnected bundles, clusters, or aggregates of CNTsor other high aspect ratio carbon materials. In some embodiments, thehigh aspect ratio carbon elements 201 may include graphene in sheet,flake, or curved flake form, and/or formed into high aspect ratio cones,rods, and the like.

In some embodiments, the electrode active layer 100 may contain littleor no bulk binder material, leaving more space in the network 200 to beoccupied by active material particles 300. For example, in someembodiments, the active layer 200 contains less than 10% by weight, lessthan 1% by weight, less than 0.1% by weight, less than 0.01% by weight,or less of binder material (e.g., polymeric or cellulosic bindermaterial) disposed in the void spaces.

For example, in some embodiments the electrode active layer is free ofor substantially free of polymeric material, or any material other thanthe active material 300, and the network 200 composed of the high aspectratio carbon elements 201 and the surface treatment 202 disposedthereon.

In some embodiments, the network 200 is composed largely or evenentirely of carbon. For example, in some embodiments the network 200 isat least 90% carbon by weight, at least 95% carbon by weight, at least96% carbon by weight, at least 97% carbon by weight, at least 98% carbonby weight at least 99% carbon by weight, at least 99.5% carbon byweight, at least 99.9% carbon by weight, or more.

In some embodiments, a size (e.g., the average size, median size, orminimum size) of the high aspect ratio carbon elements 201 forming thenetwork 200 along one or two major dimensions may be at least 0.1 μm,0.5 μm, 1 μm, 5 μm, 10 μm, 50 μm, 100 μm, 200 μm, 300, μm, 400 μm, 500μm, 600 μm, 7000 μm, 800 μm, 900 μm, 1,000 μm or more. For example, insome embodiments, the size (e.g., the average size, median size, orminimum size) of the elements 201 forming the network 200 may be in therange of 1 μm to 1,000 μm, or any subrange thereof, such as 1 μm to 600μm.

In some embodiments, the size of the elements can be relatively uniform.For example, in some embodiments, more than 50%, 60%, 70%, 80%, 90%,95%, 99% or more of the elements 201 may have a size along one or twomajor dimensions within 10% of the average size for the elements 201making up the network 200.

Applicants have found that an active layer 100 of the type herein canprovide exemplary performance (e.g., high conductivity, low resistance,high voltage performance, and high energy and power density) even whenthe mass fraction of elements 201 making up the network 200 in the layer100 is quite low, thereby allowing high mass loading of active materialparticles 300. For example, in some embodiments, the active layer 100may be at least about 50 wt % (percent by weight), 60 wt %, 70 wt %, 75wt %, 80 wt %, 85 wt %, 90 wt %, 95 wt %, 96 wt % 97 wt %, 98 wt %, 99wt %, 99.5 wt %, or more of active material particles 300.

In some embodiments, the network 200 forms an interconnected network ofhighly electrically conductive paths for current flow (e.g. electron orion transport) through the active layer 100. For example, in someembodiments, highly conductive junctions may occur at points where theelements 201 of the network intersect with each other, or where they arein close enough proximity to allow for quantum tunneling of chargecarriers (e.g., electrons or ions) from one element to the next. Whilethe elements 201 may make up a relatively low mass fraction of theactive layer (e.g., less than 10 wt %, 5 wt %, 4 wt %, 3 wt %, 2 wt %, 1wt % or less, e.g., in the range of 0.5 wt % to 10 wt % or any subrangethereof such as 1 wt % to 5.0 wt %), the interconnected network ofhighly electrically conductive paths formed in the network 200 mayprovide long conductive paths to facilitate current flow within andthrough the active layer 100 (e.g. conductive paths on the order of thethickness of the active layer 100).

For example, in some embodiments, the network 200 may include one ormore structures of interconnected elements 201, where the structure hasan overall length along one or more dimensions longer than 2, 3, 4, 5,10, 20, 50, 100, 500, 1,000, 10,000 or more times the average length ofthe component elements 201 making up the structure. For example, in someembodiments, network 200 may include one or more structures ofinterconnected elements 200, where the structure has an overall lengthin the range of 2 to 10,000 (or any subrange thereof) times the averagelength of the component elements 201 making up the structure. Forexample, in some embodiments the network 200 may include highlyconductive pathways having a length greater than 100 μm, 500 μm, 1,000μm, 10,000 μm or more, e.g., in the range of 100 μm-10,000 μm of anysubrange thereof.

As used herein, the term “highly conductive pathway” is to be understoodas a pathway formed by interconnected elements 201 having an electricalconductivity higher than the electrical conductivity of the activematerial particles enmeshed in the network 200.

Not wishing to be bound by theory, in some embodiments the network 200can characterized as an electrically interconnected network of elements201 exhibiting connectivity above a percolation threshold. Percolationthreshold is a mathematical concept related to percolation theory, whichis the formation of long-range connectivity in random systems. Below thethreshold a so called “giant” connected component of the order of systemsize does not exist; while above it, there exists a giant component ofthe order of system size.

In some embodiments, the percolation threshold can be determined byincreasing the mass fraction of elements 201 in the active layer 100while measuring the conductivity of the layer, holding all otherproperties of the layer constant. In some such cases, the threshold canbe identified with the mass fraction at which the conductivity of thelayer sharply increases and/or the mass fraction above which theconductivity of the layer increases only slowly with increases with theaddition of more elements 201. Such behavior is indicative of crossingthe threshold required for the formation of interconnected structuresthat provide conductive pathways with a length on the order of the sizeof the active layer 100.

FIG. 2 shows a detailed view of high aspect ratio carbon element 201 ofthe network 200 (as shown in FIG. 1 ), located near several activematerial particles 300. In the embodiment shown, the surface treatment202 on the element 201 is a surfactant layer bonded to the outer layerof the surface of the element 201. As shown, the surfactant layercomprises a plurality of surfactant elements 210 each having ahydrophobic end 211 and a hydrophilic end 212, wherein the hydrophobicend is disposed proximal the surface of the carbon element 201 and thehydrophilic end 212 is disposed distal the surface.

In some embodiments where the carbon element 201 is hydrophobic (as istypically the case with nanoform carbon elements such as CNTs, CNTbundles, and graphene flakes), the hydrophobic end 211 of the surfactantelement 210 will be attracted to the carbon element 201. Accordingly, insome embodiments, the surface treatment 202 may be a self-assemblinglayer. For example, as detailed below, in some embodiments, when theelements 201 are mixed in a solvent with a surfactant elements 210 toform a slurry, the surface treatment 202 layer self assembles on thesurface due to electrostatic interactions between the elements 201 and210 within the slurry.

In some embodiments, the surface treatment 202 may a self-limitinglayer. For example, as detailed below, in some embodiments, when theelements 201 are mixed in a solvent with a surfactant elements 210 toform a slurry, the surface treatment 202 layer self assembles on thesurface due to electrostatic interactions between the elements 201 and210 within the slurry. In some such embodiments, once an area of thesurface of the element 201 is covered in surfactant elements 210,additional surfactant elements 210 will not be attracted to that area.In some embodiments, once the surface of the element 201 is covered withsurfactant elements 202, further elements are repulsed from the layer,resulting in a self-limiting process. For example, in some embodimentsthe surface treatment 202 may form in a self-limiting process, therebyensuring that the layer will be thin, e.g., a single molecule or a fewmolecules thick.

In some embodiments, the hydrophilic ends 212 of at least a portion ofthe surfactant elements form bonds with the active material particles300. Accordingly, the surface treatment 202 can provide good adhesionbetween the elements 201 of the network 200 and the active materialparticles. In some embodiments, the bonds may be covalent bonds, ornon-covalent bonds such as π-π bonds, hydrogen bonds, electrostaticbonds or combinations thereof.

For example, in some embodiments, the hydrophilic end 212 of thesurfactant element 210 has a polar charge of a first polarity; while thesurface of the active material particles 300 carry a polar charge of asecond polarity opposite that of the first polarity, and so areattracted to each other.

For example, in some embodiments where, during formation of the layer100, the active material particles 300 are combined in a solvent withcarbon elements 201 bearing the surface treatment 202 (as described ingreater detail below), the outer surface of the active materialparticles 300 may be characterized by a Zeta potential (as is known inthe art) having the opposite sign of the Zeta potential of the outersurface of the surface treatment 202. Accordingly, in some suchembodiments, attractions between the carbon elements 201 bearing thesurface treatment 202 and the active material products 300 promote theself-assembly of a structure in which the active material particles 300are enmeshed with the carbon elements 201 of the network 200.

In some embodiments the hydrophilic ends 212 of at least a portion ofthe surfactant elements form bonds with a current collector layer oradhesion layer underlying the active material layer 100. Accordingly,the surface treatment 202 can provide good adhesion between the elements201 of the network 200 and such underlying layer. In some embodiments,the bonds may be covalent bonds, or non-covalent bonds such as π-πbonds, hydrogen bonds, electrostatic bonds or combinations thereof. Insome embodiments, this arrangement provides for excellent mechanicalstability of the electrode 10, as discussed in greater detail below.

In various embodiments, the surfactant used to form the surfacetreatment 202 as described above may include any suitable material. Forexample, in some embodiments the surfactant may include one or more ofthe following: hexadecyltrimethylammonium hexafluorophosphate (CTAP),hexadecyltrimethylammonium tetrafluoroborate (CTAB),hexadecyltrimethylammonium acetate, hexadecyltrimethylammonium nitrate,hocamidopropyl betaine, N-(cocoalkyl)-N,N,N-trimethylammonium methylsulfate, and cocamidopropyl betaine. Additional suitable materials aredescribed below.

In some embodiments, the surfactant layer 202 may be formed bydissolving a compound in a solvent, such that the layer of surfactant isformed from ions from the compound (e.g., in a self-limiting process asdescribed above). In some such embodiments, the active layer 100 willthen include residual counter ions 214 to the surfactant ions formingthe surface treatment 202.

In some embodiments, these surfactant counter ions 214 are selected tobe compatible with use in an electrochemical cell. For example, in someembodiments, the counter ions are selected to be unreactive or mildlyreactive with materials used in the cell, such as an electrolyte,separator, housing, or the like. For example, if an aluminum housing isused the counter ion may be selected to be unreactive or mildly reactivewith the aluminum housing.

For example, in some embodiments, the residual counter ions are free orsubstantially free of halide groups. For example, in some embodiments,the residual counter ions are free or substantially free of bromine.

In some embodiments, the residual counter ions may be selected to becompatible with an electrolyte used in an energy storage cell containingthe active layer 200. For example, in some embodiments, residual counterions maybe the same species of ions used in the electrolyte itself. Forexample, if the electrolyte includes a dissolved Li PF₆ salt, theelectrolyte anion is PF₆. In such a case, the surfactant may be selectedas, for example, CTA PF6, such that the surface treatment 202 is formedas a layer of anions from the CTA PF6, while the residual surfactantcounter ions are the PF₆ anions from the CTA PF6 (thus matching theanions of the electrolyte).

In some embodiments, the surfactant material used may be soluble in asolvent which exhibits advantageous properties. For example, in someembodiments, the solvent may include water or an alcohol such asmethanol, ethanol, or 2-propanol (isopropyl alcohol, sometimes referredto as IPA) or combinations thereof. In some embodiments, the solvent mayinclude one or more additives used to further improve the properties ofthe solvent, e.g., low boiling point additives such as acetonitrile(ACN), de-ionized water, and tetrahydrofuran.

For example, if a low boiling point solvent is used in the formation ofthe surface treatment 202, the solvent may be quickly removed using athermal drying process (e.g., of the type described in greater detailbelow) performed at a relatively low temperature. As will be understoodby those skilled in the art, this can improve the speed and or cost ofmanufacture of the active layer 202.

For example, in some embodiments, the surface treatment 202 is formedfrom a material which is soluble in a solvent having a boiling pointless than 250° C., 225° C., 202° C., 200° C., 185° C., 180° C., 175° C.,150° C., 125° C., or less, e.g., less than or equal to 100° C.

In some embodiments, the solvent may exhibit other advantageousproperties. In some embodiments the solvent may have a low viscosity,such a viscosity at 20° C. of less than or equal to 3.0 centipoise, 2.5centipoise, 2.0 centipoise, 1.5 centipoise, or less. In some embodimentsthe solvent may have a low surface tension such a surface tension at 20°C. of less than or equal to 40 mN/m, 35 mN/m, 30 mN/m, 25 mN/m or less.In some embodiments the solvent may have a low toxicity, e.g., toxicitycomparable to alcohols such as isopropyl alcohol.

Notably, this contrasts with the process used to form conventionalelectrode active layers featuring bulk binder materials such aspolyvinylidene fluoride or polyvinylidene difluoride (PVDF). Such bulkbinders require aggressive solvents often characterized by high boilingpoints. One such example is n-methyl-2-pyrrolidone (NMP). Use of NMP (orother pyrrolidone based solvents) as a solvent requires the use of hightemperate drying processes to remove the solvent. Moreover, NMP isexpensive, requiring a complex solvent recovery system, and highlytoxic, posing significant safety issues. In contrast, as furtherdetailed below, in various embodiments the active layer 200 may beformed without the use of NMP or similar compounds such pyrrolidonecompounds.

While one class of exemplary surface treatment 202 is described above,it is understood that other treatments may be used. For example, invarious embodiments the surface treatment 202 may be formed byfunctionalizing the high aspect ratio carbon elements 201 using anysuitable technique as described herein or known in the art. Functionalgroups applied to the elements 201 may be selected to promote adhesionbetween the active material particles 300 and the network 200. Forexample, in various embodiments the functional groups may includecarboxylic groups, hydroxylic groups, amine groups, silane groups, orcombinations thereof

As will be described in greater detail below, in some embodiments, thefunctionalized carbon elements 201 are formed from dried (e.g.,lyophilized) aqueous dispersion comprising nanoform carbon andfunctionalizing material such as a surfactant. In some such embodiments,the aqueous dispersion is substantially free of materials that woulddamage the carbon elements 201, such as acids.

Referring to FIG. 3 , in some embodiments, the surface treatment 202 onthe high aspect ratio carbon elements 201 includes a thin polymericlayer disposed on the carbon elements that promotes adhesion of theactive material to the network. In some such embodiments the thinpolymeric layer comprises a self-assembled and or self-limiting polymerlayer. In some embodiments, the thin polymeric layer bonds to the activematerial, e.g., via hydrogen bonding.

In some embodiments the thin polymeric layer may have a thickness in thedirection normal to the outer surface of the carbon elements of lessthat 3 times, 2 times, 1 times, 0.5 times, 0.1 times that the minordimension of the element 201 (or less).

In some embodiments, the thin polymeric layer includes functional groups(e.g., side functional groups) that bond to the active material, e.g.,via non-covalent bonding such a π-π bonding. In some such embodimentsthe thin polymeric layer may form a stable covering layer over at leasta portion of the elements 201.

In some embodiments, the thin polymeric layer on some of the elements201 may bond with a current collector 101 or adhesion layer 102underlying the active layer 200. For example, in some embodiments thethin polymeric layer includes side functional groups that bond to thesurface of the current collector 101 or adhesion layer 102, e.g., vianon-covalent bonding such a π-π bonding. in some such embodiments thethin polymeric layer may form a stable covering layer over at least aportion of the elements 201. In some embodiments, this arrangementprovides for excellent mechanical stability of the electrode 10, asdiscussed in greater detail below.

In some embodiments, the polymeric material is miscible in solvents ofthe type described in the examples above. For example, in someembodiments the polymeric material is miscible in a solvent thatincludes an alcohol such as methanol, ethanol, or 2-propanol (isopropylalcohol, sometimes referred to as IPA) or combinations thereof. In someembodiments, the solvent may include one or more additives used tofurther improve the properties of the solvent, e.g., low boiling pointadditives such as acetonitrile (ACN), de-ionized water, andtetrahydrofuran.

Suitable examples of materials which may be used to form the polymericlayer include water soluble polymers such as polyvinylpyrrolidone.Additional exemplary materials are provided below.

In some embodiments, the polymeric material has a low molecular mass,e.g., less than or equal to 1,000,000 g/mol, 500,000 g/mol, 100,000g/mol, 50,000 g/mol, 10,000 g/mol, 5,000 g/mol, 2,500 g/mol or less.

Note that the thin polymeric layer described above is qualitativelydistinct from bulk polymer binder used in conventional electrodes.Rather than filling a significant portion of the volume of the activelayer 100, the thin polymeric layer resides on the surface of the highaspect ratio carbon elements, leaving the vast majority of the voidspace withing the network 200 available to hold active materialparticles 300.

For example, in some embodiments, the thin polymeric layer has a maximumthickness in a direction normal to an outer surface of the network ofless than or equal to 1 times, 0.5 times, 0.25 times, or less of thesize of the carbon elements 201 along their minor dimensions. Forexample, in some embodiments the thin polymeric layer may be only a fewmolecules thick (e.g., less than or equal to 100, 50, 10, 5, 4, 3, 2, oreven 1 molecule(s) thick). Accordingly, in some embodiments, less than10%, 5%, 1%, 0.1%, 0.01%, 0.001% or less of the volume of the activelayer 100 is filled with the thin polymeric layer.

In yet further exemplary embodiments, the surface treatment 202 may beformed a layer of carbonaceous material which results from thepyrolization of polymeric material disposed on the high aspect ratiocarbon elements 201. This layer of carbonaceous material (e.g.,graphitic or amorphous carbon) may attach (e.g., via covalent bonds) toor otherwise promote adhesion with the active material particles 300.Examples of suitable pyrolization techniques are described in U.S.Patent Application Ser. No. 63/028,982 filed May 22, 2020. One suitablepolymeric material for use in this technique is polyacrylonitrile (PAN).

In various embodiments, the active material particles 300 may includeany active material suitable for use in energy storage devices,including metal oxides such as lithium metal oxides.

For example, the active material particles 300 may include lithiumcobalt oxide (LCO, sometimes called “lithium cobaltate” or “lithiumcobaltite,” is a chemical compound with one variant of possibleformulations being LiCoO₂); lithium nickel manganese cobalt oxide (NMC,with a variant formula of LiNiMnCo); lithium manganese oxide (LMO withvariant formulas of LiMn₂O₄, Li₂MnO₃ and others); lithium nickel cobaltaluminum oxide (LiNiCoAlO₂ and variants thereof as NCA) and lithiumtitanate oxide (LTO, with one variant formula being Li₄Ti₅O₁₂); lithiumiron phosphate oxide (LFP, with one variant formula being LiFePO₄),lithium nickel cobalt aluminum oxide (and variants thereof as NCA) aswell as other similar other materials. Other variants of the foregoingmay be included.

In some embodiments where NMC is used as an active material, nickel richNMC may be used. For example, in some embodiments, the variant of NMCmay be LiNi_(x)Mn_(y)Co_(1-x-y), where x is equal to or greater thanabout 0.7, 0.75, 0.80, 0.85, or more. In some embodiments, so calledNMC811 may be used, where in the foregoing formula x is about 0.8 and yis about 0.1.

In some embodiments, the active material includes other forms of LithiumNickel Manganese Cobalt Oxide (LiNi_(x)Mn_(y)Co_(z)O₂). For example,common variants such as, without limitation: NMC 111(LiNi_(0.33)Mn_(0.33)Co_(0.33)O₂); NMC 532(LiNi_(0.5)Mn_(0.3)Co_(0.2)O₂); NMC 622 (LiNi_(0.6)Mn_(0.2)Co_(0.2)O₂);and others may be used.

In some embodiments, e.g., where the electrode is used as an anode, theactive material may include graphite, hard carbon, activated carbon,nanoform carbon, silicon, silicon oxides, carbon encapsulated siliconnanoparticles. In some such embodiments the active layer 100 may beintercalated with lithium, e.g., using pre-lithiation methods known inthe art.

In some embodiments, the techniques described herein may allow for theactive layer 100 be made of in large portion of material in the activelayer, e.g., greater than 75%, 80%, 85%, 90%, 95%, 99%, 99.5%, 99.8% ormore by weight, while still exhibiting excellent mechanical properties(e.g., lack of delamination during operation in an energy storage deviceof the types described herein). For example, in some embodiments, theactive layer may have such aforementioned high amount of active materialand a large thickness (e.g., greater than 50 nm, 100 nm, 150 nm, 200 nm,or more), while still exhibiting excellent mechanical properties (e.g.,a lack of delamination during operation in an energy storage device ofthe types described herein).

The active material particles 201 in the active layer 100 may becharacterized by a median particle sized in the range of e.g., 0.1 μmand 50 micrometers μm, or any subrange thereof. The active materialparticles 201 in the active layer 100 may be characterized by a particlesized distribution which is monomodal, bi-modal or multi-modal particlesize distribution. The active material particles 201 may have a specificsurface area in the range of 0.1 meters squared per gram (m²/g) and 100meters squared per gram (m²/g), or any subrange thereof.

In some embodiments, the active layer 100 may have mass loading ofactive material particles 300 e.g., of at least 20 mg/cm², 30 mg/cm², 40mg/cm², 50 mg/cm², 60 mg/cm², 70 mg/cm², 80 mg/cm², 90 mg/cm², 100mg/cm², or more.

Referring to FIG. 4 , an electron micrograph of an exemplary activematerial layer of the type described herein is shown. Tendril like highaspect ratio carbon elements 201 (formed of CNT bundles) are clearlyshown enmeshing the active material particles 300. Note the lack of anybulky polymeric material taking up space within the layer.

Energy Storage Cell

Referring to FIG. 5 , an energy storage cell 500 is shown which includesa first electrode 501 a second electrode 502, a permeable separator 503disposed between the first electrode 501 and the second electrode 502,and an electrolyte 504 wetting the first and second electrodes. One orboth of the electrodes 501, 502 may be of the type described herein.

In some embodiments, the energy storage cell 500 may be a battery, suchas a lithium ion battery. In some such embodiments, the electrolyte maybe a lithium salt dissolved in a solvent, e.g., of the types describedin Qi Li, Juner Chen, Lei Fan, Xueqian Kong, Yingying Lu, Progress inelectrolytes for rechargeable Li-based batteries and beyond, GreenEnergy & Environment, Volume 1, Issue 1, Pages 18-42, the entirecontents of which are incorporated herein by reference.

In some such embodiments, the energy storage cell may have anoperational voltage in the range of 1.0 V to 5.0 V, or any subrangethereof such as 2.3V-4.3V.

In some such embodiments, the energy storage cell 500 may have anoperating temperature range comprising −40° C. to 100° C. or anysubrange thereof such as −10° C. to 60° C.

In some such embodiments, the energy storage cell 500 may have agravimetric energy density of at least 100 Wh/kg, 200 Wh/kg, 300 Wh/kg,400 Wh/kg, 500 Wh/kg, 1000 Wh/kg or more.

In some such embodiments, the energy storage cell 500 may have avolumetric energy density of at least 200 Wh/L, 400 Wh/L, 600 Wh/L, 800Wh/L, 1,000 Wh/L, 1,500 Wh/L, 2,000 Wh/L or more.

In some such embodiments, the energy storage cell 500 may have a C ratein the range of 0.1 to 50.

In some such embodiments, the energy storage cell 500 may have a cyclelife of at least 1,000, 1500, 2,000, 2,500, 3,000, 3,500, 4,000 or morecharge discharge cycles.

In some embodiments, the energy storage cell 500 may be a lithium ioncapacitor of the type described in U.S. Pat. App. Ser. No. 63/021,492,filed May 8, 2020, the entire contents of which are incorporated hereinby reference.

In some such embodiments, the energy storage cell 500 may have anoperating temperature range comprising −60° C. to 100° C. or anysubrange thereof such as −40° C. to 85° C.

In some such embodiments, the energy storage cell 500 may have agravimetric energy density of at least 10 Wh/kg, 15 Wh/kg, 20 Wh/kg, 30Wh/kg, 40 Wh/kg, 50 Wh/kg, or more.

In some such embodiments, the energy storage cell 500 may have avolumetric energy density of at least 20 Wh/L, 30 Wh/L, 40 Wh/L, 50Wh/L, 60 Wh/L, 70 Wh/L, 80 Wh/L or more.

In some such embodiments, the energy storage cell 500 may have agravimetric power density of at least 5 kW/kg, 7.5 W/kg, 10 kW/kg, 12.5kW/kg, 14 kW/kg, 15 kW/kg or more.

In some such embodiments, the energy storage cell 500 may have avolumetric power density of at least 10 kW/L, 15 kW/L, 20 kW/L, 22.5kW/L, 25 kW/L, 28 kW/L, 30 kW/L or more.

In some such embodiments, the energy storage cell 500 may have a C ratein the range of 1.0 to 100.

In some such embodiments, the energy storage cell 500 may have a cyclelife of at least 100,000, 500,000, 1,000,000 or more charge dischargecycles.

Fabrication Methods

The electrode 10 featuring active layer 100 as described herein may bemade using any suitable manufacturing process. As will be understood byone skilled in the art, in some embodiments the electrode 10 may be madeusing wet coating techniques of the types described in InternationalPatent Publication No. WO/2018/102652 published Jun. 7, 2018 in furtherview of the teachings described herein.

Referring to FIG. 6 , in some embodiments, the active layer 100 ofelectrode 10 may be formed using the method 1000. In step 1001 highaspect ratio carbon elements 201 and a surface treatment material (e.g.,a surfactant or polymer material as described herein) are combined witha solvent (of the type described herein) to form an initial slurry.

In step 1002 the initial slurry is processed to ensure good dispersionof the solid materials in the slurry. In some embodiments, thisprocessing includes introducing mechanical energy into the mixture ofsolvent and solid materials (e.g., using a sonicator, which may besometimes also be referred to as a “sonifier”) or other suitable mixingdevice (e.g., a high shear mixer). In some embodiments, the mechanicalenergy introduced into the mixture is at least 0.4 kilowatt-hours perkilogram (kWh/kg), 0.5 kWh/kg, 0.6 kWh/kg, 0.7 kWh/kg, 0.8 kWh/kg, 0.9kWh/kg, 1.0 kWh/kg, or more. For example, the mechanical energyintroduced into the mixture per kilogram of mixture may be in the rangeof 0.4 kWh/kg to 1.0 kWh/kg or any subrange thereof such as 0.4 kWh/kgto 0.6 kWh/kg.

In some embodiments an ultrasonic bath mixer may be used. In otherembodiments, a probe sonicator may be used. Probe sonication may besignificantly more powerful and effective when compared to ultrasonicbaths for nanoparticle applications. High shear forces created byultrasonic cavitation have the ability to break up particle agglomeratesand result in smaller and more uniform particles sizes. Among otherthings, sonication can result in stable and homogenous suspensions ofthe solids in the slurry. Generally, this results in dispersing anddeagglomerating and other breakdown of the solids. Examples of probesonication devices include the Q Series Probe Sonicators available fromQSonica LLC of Newtown, Connecticut. Another example includes theBranson Digital SFX-450 sonicator available commercially from ThomasScientific of Swedesboro, New Jersey.

In some embodiments, however, the localized nature of each probe withinthe probe assembly can result in uneven mixing and suspension. Such maybe the case, for example, with large samples. This may be countered byuse of a setup with a continuous flow cell and proper mixing. That is,with such a setup, mixing of the slurry will achieve reasonably uniformdispersion.

In some embodiments the initial slurry, once processed will have aviscosity in the range of 5,000 cps to 25,000 cps or any subrangethereof, e.g., 6,000 cps to 19,000 cps.

In step 1003, the surface treatment 202 may be fully or partially formedon the high aspect ratio carbon elements 201 in the initial slurry. Insome embodiments, at this stage the surface treatment 202 mayself-assemble as described in detail above with reference to FIGS. 2 and3 . The resulting surface treatment 201 may include functional groups orother features which, as described in further steps below, may promoteadhesion between the high aspect ratio carbon elements 201 and activematerial particles 300.

In step 1004 the active material particles 300 may be combined with theinitial slurry to form a final slurry containing the active materialparticles 300 along with the high aspect ratio carbon elements 201 withthe surface treatment 202 formed thereon.

In some embodiments, the active material 300 may be added directly tothe initial slurry. In other embodiments, the active material 300 mayfirst be dispersed in a solvent (e.g., using the techniques describedabove with respect to the initial solvent) to form an active materialslurry. This active material slurry may then be combined with theinitial slurry to form the final slurry.

In step 1005 the final slurry is processed to ensure good dispersion ofthe solid materials in the final slurry. In various embodiments anysuitable mixing process known in the art may be used. In someembodiments this processing may use the techniques described above withreference to step 1002. In some embodiments, a planetary mixer such as amulti-axis (e.g., three or more axis) planetary mixer may be used. Insome such embodiments the planetary mixer can feature multiple blades,e.g., two or more mixing blades and one or more (e.g., two, three, ormore) dispersion blades such as disk dispersion blades.

In some embodiments, during this step 1005, the matrix 200 enmeshing theactive material 300 may fully or partially self-assemble, as describedin detail above with reference to FIGS. 2 and 3. In some embodiments,interactions between the surface treatment 202 and the active material300 promote the self-assembly process.

In some embodiments the final slurry, once processed will have aviscosity in the range of 1,000 cps to 10,000 cps or any subrangethereof, e.g., 2,500 cps to 6000 cps

In step 1006, the active layer 100 is formed from the final slurry. Insome embodiments, final slurry may be cast wet directly onto the currentcollector conductive layer 101 (or optional adhesion layer 102) anddried. As an example, casting may be by applying at least one of heatand a vacuum until substantially all of the solvent and any otherliquids have been removed, thereby forming the active layer 100. In somesuch embodiments it may be desirable to protect various parts of theunderlying layers. For example, it may desirable to protect an undersideof the conductive layer 101 where the electrode 10 is intended fortwo-sided operation. Protection may include, for example, protectionfrom the solvent by masking certain areas, or providing a drain todirect the solvent away.

In other embodiments, the final slurry may be at least partially driedelsewhere and then transferred onto the adhesion layer 102 or theconductive layer 101 to form the active layer 100, using any suitabletechnique (e.g., roll-to-roll layer application). In some embodimentsthe wet combined slurry may be placed onto an intermediate material withan appropriate surface and dried to form the layer (i.e., the activelayer 100). While any material with an appropriate surface may be usedas the intermediate material, exemplary intermediate material includesPTFE as subsequent removal from the surface is facilitated by theproperties thereof. In some embodiments, the designated layer is formedin a press to provide a layer that exhibits a desired thickness, areaand density.

In some embodiments, the final slurry may be formed into a sheet, andcoated onto the adhesion layer 102 or the conductive layer 101 asappropriate. For example, in some embodiments, the final slurry may beapplied to through a slot die to control the thickness of the appliedlayer. In other embodiments, the slurry may be applied and then leveledto a desired thickness, e.g., using a doctor blade. A variety of othertechniques may be used for applying the slurry. For example, coatingtechniques may include, without limitation: comma coating; comma reversecoating; doctor blade coating; slot die coating; direct gravure coating;air doctor coating (air knife); chamber doctor coating; off set gravurecoating; one roll kiss coating; reverse kiss coating with a smalldiameter gravure roll; bar coating; three reverse roll coating (topfeed); three reverse roll coating (fountain die); reverse roll coatingand others.

The viscosity of the final slurry may vary depending on the applicationtechnique. For example, for comma coating, the viscosity may rangebetween about 1,000 cps to about 200,000 cps. Lip-die coating providesfor coating with slurry that exhibits a viscosity of between about 500cps to about 300,000 cps. Reverse-kiss coating provides for coating withslurry that exhibits a viscosity of between about 5 cps and 1,000 cps.In some applications, a respective layer may be formed by multiplepasses.

In some embodiments, the active layer 100 formed from the final slurrymay be compressed (e.g., using a calendaring apparatus) before or afterbeing applied to the electrode 10. In some embodiments, the slurry maybe partially or completely dried (e.g., by applying heat, vacuum or acombination thereof) prior to or during the compression process. Forexample, in some embodiments, the active layer may be compressed to afinal thickness (e.g., in the direction normal to the current collectorlayer 101) of less than 90%, 80%, 70%, 50%, 40%, 30%, 20%, 10% or lessof its pre-compression thickness.

In various embodiments, when a partially dried layer is formed during acoating or compression process, the layer may be subsequently fullydried, (e.g., by applying heat, vacuum or a combination thereof). Insome embodiments, substantially all of the solvent is removed from theactive layer 100.

In some embodiments, solvents used in formation of the slurries arerecovered and recycled into the slurry-making process.

In some embodiments, the active layer may be compressed, e.g., to breaksome of the constituent high aspect ratio carbon elements or othercarbonaceous material to increase the surface area of the respectivelayer. In some embodiments, this compression treatment may increase oneor more of adhesion between the layers, ion transport rate within thelayers, and the surface area of the layers. In various embodiments,compression can be applied before or after the respective layer isapplied to or formed on the electrode 10.

In some embodiments where calendaring is used to compress the activelayer 100, the calendaring apparatus may be set with a gap spacing equalto less than 90%, 80%, 70%, 50%, 40%, 30%, 20%, 10% or less of thelayer's pre-compression thickness (e.g., set to about 33% of the layer'spre-compression thickness). The calendar rolls can be configured toprovide suitable pressure, e.g., greater than 1 ton per cm of rolllength, greater than 1.5 ton per cm of roll length, greater than 2.0 tonper cm of roll length, greater than 2.5 ton per cm of roll length, ormore. In some embodiments, the post compression active layer will have adensity in the range of 1 g/cc to 10 g/cc, or any subrange thereof suchas 2.5 g/cc to 4.0 g/cc. In some embodiments the calendaring process maybe carried out at a temperature in the range of 20° C. to 140° C. or anysubrange thereof. In some embodiments the active layer may be pre-heatedprior to calendaring, e.g., at a temperature in the range of 20° C. to100° C. or any subrange thereof.

Once the electrode 10 has been assembled, the electrode 100 may be usedto assemble the energy storage device 10. Assembly of the energy storagedevice 10 may follow conventional steps used for assembling electrodeswith separators and placement within a housing such as a canister orpouch, and further may include additional steps for electrolyte additionand sealing of the housing.

In various embodiments, process 1000 may include any of the followingfeatures (individually or in any suitable combination)

In some embodiments, the initial slurry has a solid content in the rangeof 0.1%-20.0% (or any subrange thereof) by weight. In some embodiments,the final slurry has a solid content in the range of 10.0%-80% (or anysubrange thereof) by weight.

In various embodiments, the solvent used may any of those describedherein with respect to the formation of the surface treatment 202. Insome embodiments, the surfactant material used to form the surfacetreatment 202 may be soluble in a solvent which exhibits advantageousproperties. For example, in some embodiments, the solvent may includewater or an alcohol such as methanol, ethanol, or 2-propanol (isopropylalcohol, sometimes referred to as IPA) or combinations thereof. In someembodiments, the solvent may include one or more additives used tofurther improve the properties of the solvent, e.g., low boiling pointadditives such as acetonitrile (ACN), de-ionized water, andtetrahydrofuran.

In some embodiments, if a low boiling point solvent is used the solventmay be quickly removed using a thermal drying process performed at arelatively low temperature. As will be understood by those skilled inthe art, this can improve the speed and or cost of manufacture of theelectrode 10. For example, in some embodiments, the solvent may have aboiling point less than 250° C., 225° C., 202° C., 200° C., 185° C.,180° C., 175° C., 150° C., 125° C., or less, e.g., less than or equal to100° C.

In some embodiments, the solvent may exhibit other advantageousproperties. In some embodiments the solvent may have a low viscosity,such a viscosity at 20° C. of less than or equal to 3.0 centipoise, 2.5centipoise, 2.0 centipoise, 1.5 centipoise, or less. In some embodimentsthe solvent may have a low surface tension such a surface tension at 20°C. of less than or equal to 40 mN/m, 35 mN/m, 30 mN/m, 25 mN/m or less.In some embodiments the solvent may have a low toxicity, e.g., toxicitycomparable to alcohols such as isopropyl alcohol.

In some embodiments, during the formation of the active layer, amaterial forming the surface treatment may be dissolved in a solventsubstantially free of pyrrolidone compounds. In some embodiments, thesolvent is substantially free of n-methyl-2-pyrrolidone.

In some embodiments, the surface treatment 201 is formed from a materialthat includes a surfactant of the type described herein.

In some embodiments, dispersing high aspect ratio carbon elements and asurface treatment material in a solvent to form an initial slurrycomprises applying forces to agglomerated carbon elements to cause theelements to slide apart from each other along a direction transverse toa minor axis of the elements. In some embodiments, techniques forforming such dispersions may be adapted from those disclosed inInternational Patent Publication No. WO/2018/102652 published Jun. 7,2018 in further view of the teachings described herein.

In some embodiments, the high aspect ratio carbon elements 201 can befunctionalized prior to forming a slurry used to form the electrode 10.For example, in one aspect a method is disclosed that includesdispersing high aspect ratio carbon elements 201 and a surface treatmentmaterial in an aqueous solvent to form an initial slurry, wherein saiddispersion step results in the formation of a surface treatment on thehigh aspect ratio carbon; drying the initial slurry to removesubstantially all moisture resulting in a dried powder of the highaspect ratio carbon with the surface treatment thereon. In someembodiments, the dried powder may be combined, e.g., with a slurry ofsolvent and active material to form a final solvent of the typedescribed above with reference to method 1000.

In some embodiments, drying the initial slurry comprises lyophilizing(freeze-drying) the initial slurry. In some embodiments, the aqueoussolvent and initial slurry are substantially free of substances damagingto the high aspect ratio carbon elements. In some embodiments, theaqueous solvent and initial slurry are substantially free of acids. Insome embodiments, the initial slurry consists essentially of the highaspect ratio carbon elements, the surface treatment material, and water.

Some embodiments further include dispersing the dried powder of the highaspect ratio carbon with the surface treatment in a solvent and addingand active material to form a secondary slurry; coating the secondaryslurry onto a substrate; and drying the secondary slurry to form anelectrode active layer. In some embodiments, the preceding steps can beperformed using techniques adapted from those disclosed in InternationalPatent Publication No. WO/2018/102652 published Jun. 7, 2018 in furtherview of the teachings described herein.

In some embodiments, the final slurry may include polymer additives suchas polyacrilic acid (PAA), poly(vinyl alcohol) (PVA), poly(vinylacetate) (PVAc), polyacrylonitrile (PAN), polyisoprene (Plpr),polyaniline (PANi), polyethylene (PE), polyimide (PI), polystyrene (PS),polyurethane (PU), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP).In some embodiments, the active layer may be treated by applying heat topyrolyze the additive such that the surface treatment 202 may be formeda layer of carbonaceous material which results from the pyrolization ofthe polymeric additive. This layer of carbonaceous material (e.g.,graphitic or amorphous carbon) may attach (e.g., via covalent bonds) toor otherwise promote adhesion with the active material particles 300.The heat treatment may be applied by any suitable means, e.g., byapplication of a laser beam. Examples of suitable pyrolizationtechniques are described in U.S. Patent Application Ser. No. 63/028,982filed May 22, 2020.

Surfactants

The techniques described above include the use of surfactants to for asurface treatment 202 on high aspect ratio carbon nanotubes 201 in orderto promote adhesion with the active material particles 300. Whileseveral advantageously suitable surfactants have been described, it isto be understood that other surfactant material may be used, includingthe following.

Surfactants are molecules or groups of molecules having surfaceactivity, including wetting agents, dispersants, emulsifiers,detergents, and foaming agents. A variety of surfactants can be used inpreparation surface treatments as described herein. Typically, thesurfactants used contain a lipophilic nonpolar hydrocarbon group and apolar functional hydrophilic group. The polar functional group can be acarboxylate, ester, amine, amide, imide, hydroxyl, ether, nitrile,phosphate, sulfate, or sulfonate. The surfactants can be used alone orin combination. Accordingly, a combination of surfactants can includeanionic, cationic, nonionic, zwitterionic, amphoteric, and ampholyticsurfactants, so long as there is a net positive or negative charge inthe head regions of the population of surfactant molecules. In someinstances, a single negatively charged or positively charged surfactantis used in the preparation of the present electrode compositions.

A surfactant used in preparation of the present electrode compositionscan be anionic, including, but not limited to, sulfonates such as alkylsulfonates, alkylbenzene sulfonates, alpha olefin sulfonates, paraffinsulfonates, and alkyl ester sulfonates; sulfates such as alkyl sulfates,alkyl alkoxy sulfates, and alkyl alkoxylated sulfates; phosphates suchas monoalkyl phosphates and dialkyl phosphates; phosphonates;carboxylates such as fatty acids, alkyl alkoxy carboxylates,sarcosinates, isethionates, and taurates. Specific examples ofcarboxylates are sodium oleate, sodium cocoyl isethionate, sodium methyloleoyl taurate, sodium laureth carboxylate, sodium tridecethcarboxylate, sodium lauryl sarcosinate, lauroyl sarcosine, and cocoylsarcosinate. Specific examples of sulfates include sodium dodecylsulfate (SDS), sodium lauryl sulfate, sodium laureth sulfate, sodiumtrideceth sulfate, sodium tridecyl sulfate, sodium cocyl sulfate, andlauric monoglyceride sodium sulfate.

Suitable sulfonate surfactants include, but are not limited to, alkylsulfonates, aryl sulfonates, monoalkyl and dialkyl sulfosuccinates, andmonoalkyl and dialkyl sulfosuccinamates. Each alkyl group independentlycontains about two to twenty carbons and can also be ethoxylated with upto about 8 units, preferably up to about 6 units, on average, forexample, 2, 3, or 4 units, of ethylene oxide, per each alkyl group.Illustrative examples of alky and aryl sulfonates are sodium tridecylbenzene sulfonate (STBS) and sodium dodecylbenzene sulfonate (SDBS).

Illustrative examples of sulfosuccinates include, but are not limitedto, dimethicone copolyol sulfosuccinate, diamyl sulfosuccinate, dicaprylsulfosuccinate, dicyclohexyl sulfosuccinate, diheptyl sulfosuccinate,dihexyl sulfosuccinate, diisobutyl sulfosuccinate, dioctylsulfosuccinate, C12-15 pareth sulfosuccinate, cetearyl sulfosuccinate,cocopolyglucose sulfosuccinate, cocoyl butyl gluceth-10 sulfosuccinate,deceth-5 sulfosuccinate, deceth-6 sulfosuccinate, dihydroxyethylsulfosuccinylundecylenate, hydrogenated cottonseed glyceridesulfosuccinate, isodecyl sulfosuccinate, isostearyl sulfosuccinate,laneth-5 sulfosuccinate, laureth sulfosuccinate, laureth-12sulfosuccinate, laureth-6 sulfosuccinate, laureth-9 sulfosuccinate,lauryl sulfosuccinate, nonoxynol-10 sulfosuccinate, oleth-3sulfosuccinate, oleyl sulfosuccinate, PEG-10 laurylcitratesulfosuccinate, sitosereth-14 sulfosuccinate, stearyl sulfosuccinate,tallow, tridecyl sulfosuccinate, ditridecyl sulfosuccinate, bisglycolricinosulfosuccinate, di(1,3-di-methylbutyl)sulfosuccinate, and siliconecopolyol sulfosuccinates.

Illustrative examples of sulfosuccinamates include, but are not limitedto, lauramido-MEA sulfosuccinate, oleamido PEG-2 sulfosuccinate,cocamido MIPA-sulfosuccinate, cocamido PEG-3 sulfosuccinate,isostearamido MEA-sulfosuccinate, isostearamido MIPA-sulfosuccinate,lauramido MEA-sulfosuccinate, lauramido PEG-2 sulfosuccinate, lauramidoPEG-5 sulfosuccinate, myristamido MEA-sulfosuccinate, oleamidoMEA-sulfosuccinate, oleamido PIPA-sulfosuccinate, oleamido PEG-2sulfosuccinate, palmitamido PEG-2 sulfosuccinate, palmitoleamido PEG-2sulfosuccinate, PEG-4 cocamido MIPA-sulfosuccinate, ricinoleamidoMEA-sulfosuccinate, stearamido MEA-sulfosuccinate, stearylsulfosuccinamate, tallamido MEA-sulfosuccinate, tallow sulfosuccinamate,tallowamido MEA-sulfosuccinate, undecylenamido MEA-sulfosuccinate,undecylenamido PEG-2 sulfosuccinate, wheat germamido MEA-sulfosuccinate,and wheat germamido PEG-2 sulfosuccinate.

Some examples of commercial sulfonates are AEROSOL® OT-S, AEROSOL®OT-MSO, AEROSOL® TR70% (Cytec Inc., West Paterson, N.J.), NaSul CA-HT3(King Industries, Norwalk, Conn.), and C500 (Crompton Co., West Hill,Ontario, Canada). AEROSOL® OT-S is sodium dioctyl sulfosuccinate inpetroleum distillate. AEROSOL® OT-MSO also contains sodium dioctylsulfosuccinate. AEROSOL® TR70% is sodium bistridecyl sulfosuccinate inmixture of ethanol and water. NaSul CA-HT3 is calcium dinonylnaphthalenesulfonate/carboxylate complex. C500 is an oil soluble calcium sulfonate.

Alkyl or alkyl groups refers to saturated hydrocarbons having one ormore carbon atoms, including straight-chain alkyl groups (for example,methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl,decyl, and so on), cyclic alkyl groups (or cycloalkyl or alicyclic orcarbocyclic groups) (for example, cyclopropyl, cyclopentyl, cyclohexyl,cycloheptyl, cyclooctyl, and so on), branched-chain alkyl groups (forexample, isopropyl, tert-butyl, sec-butyl, isobutyl, and so on), andalkyl-substituted alkyl groups (for example, alkyl-substitutedcycloalkyl groups and cycloalkyl-substituted alkyl groups).

Alkyl can include both unsubstituted alkyls and substituted alkyls.Substituted alkyls refers to alkyl groups having substituents replacingone or more hydrogens on one or more carbons of the hydrocarbonbackbone. Such substituents can include, alkenyl, alkynyl, halogeno,hydroxyl, alkylcarbonyloxy, arylcarbonyloxy, alkoxycarbonyloxy, aryloxy,aryloxycarbonyloxy, carboxylate, alkylcarbonyl, arylcarbonyl,alkoxycarbonyl, aminocarbonyl, alkyl aminocarbonyl,dialkylaminocarbonyl, alkylthiocarbonyl, alkoxyl, phosphate,phosphonato, phosphinato, cyano, amino (including alkyl amino,dialkylamino, arylamino, diarylamino and alkylarylamino), acylamino(including alkylcarbonylamino, arylcarbonylamino, carbamoyl and ureido),imino, sulfhydryl, alkylthio, arylthio, thiocarboxylate, sulfates,alkylsulfinyl, sulfonates, sulfamoyl, sulfonamido, nitro,trifluoromethyl, cyano, azido, heterocyclic, alkylaryl or aromatic(including heteroaromatic) groups.

In some embodiments, substituted alkyls can include a heterocyclicgroup. Heterocyclic groups include closed ring structures analogous tocarbocyclic groups in which one or more of the carbon atoms in the ringis an element other than carbon, for example, nitrogen, sulfur oroxygen. Heterocyclic groups can be saturated or unsaturated. Exemplaryheterocyclic groups include, aziridine, ethylene oxide (epoxides,oxiranes), thiirane (episulfides), dioxirane, azetidine, oxetane,thietane, dioxetane, dithietane, dithiete, azolidine, pyrrolidine,pyrroline, oxolane, dihydrofuran and furan.

For an anionic surfactant, the counter ion is typically sodium but canalternatively be potassium, lithium, calcium, magnesium, ammonium,amines (primary, secondary, tertiary or quandary) or other organicbases. Exemplary amines include isopropylamine, ethanolamine,diethanolamine, and triethanolamine. Mixtures of the above cations canalso be used.

A surfactant used in preparation of the present materials can becationic. Such cationic surfactants include, but are not limited to,pyridinium-containing compounds, and primary, secondary tertiary orquaternary organic amines. For a cationic surfactant, the counter ioncan be, for example, chloride, bromide, methosulfate, ethosulfate,lactate, saccharinate, acetate and phosphate. Examples of cationicamines include polyethoxylated oleyl/stearyl amine, ethoxylated tallowamine, cocoalkylamine, oleylamine and tallow alkyl amine, as well asmixtures thereof.

Examples of quaternary amines with a single long alkyl group arecetyltrimethyl ammonium bromide (CTAB), benzyldodecyldimethylammoniumbromide (BddaBr), benzyldimethylhexadecylammonium chloride (BdhaCl),dodecyltrimethylammonium bromide, myristyl trimethyl ammonium bromide,stearyl dimethyl benzyl ammonium chloride, oleyl dimethyl benzylammonium chloride, lauryl trimethyl ammonium methosulfate (also known ascocotrimonium methosulfate), cetyl-dimethyl hydroxyethyl ammoniumdihydrogen phosphate, bassuamidopropylkonium chloride, cocotrimoniumchloride, distearyldimonium chloride, wheat germ-amidopropalkoniumchloride, stearyl octyidimonium methosulfate, isostearaminopropal-koniumchloride, dihydroxypropyl PEG-5 linoleammonium chloride, PEG-2stearmonium chloride, behentrimonium chloride, dicetyl dimoniumchloride, tallow trimonium chloride and behenamidopropyl ethyl dimoniumethosulfate.

Examples of quaternary amines with two long alkyl groups aredidodecyldimethylammonium bromide (DDAB), distearyldimonium chloride,dicetyl dimonium chloride, stearyl octyldimonium methosulfate,dihydrogenated palmoylethyl hydroxyethylmonium methosulfate,dipalmitoylethyl hydroxyethylmonium methosulfate, dioleoylethylhydroxyethylmonium methosulfate, and hydroxypropyl bisstearyldimoniumchloride.

Quaternary ammonium compounds of imidazoline derivatives include, forexample, isostearyl benzylimidonium chloride, cocoyl benzyl hydroxyethylimidazolinium chloride, cocoyl hydroxyethylimidazolinium PG-chloridephosphate, and stearyl hydroxyethylimidonium chloride. Otherheterocyclic quaternary ammonium compounds, such as dodecylpyridiniumchloride, amprolium hydrochloride (AH), and benzethonium hydrochloride(BH) can also be used.

A surfactant used in preparation of the present materials can benonionic, including, but not limited to, polyalkylene oxide carboxylicacid esters, fatty acid esters, fatty alcohols, ethoxylated fattyalcohols, poloxamers, alkanolamides, alkoxylated alkanolamides,polyethylene glycol monoalkyl ether, and alkyl polysaccharides.Polyalkylene oxide carboxylic acid esters have one or two carboxylicester moieties each with about 8 to 20 carbons and a polyalkylene oxidemoiety containing about 5 to 200 alkylene oxide units. An ethoxylatedfatty alcohol contains an ethylene oxide moiety containing about 5 to150 ethylene oxide units and a fatty alcohol moiety with about 6 toabout 30 carbons. The fatty alcohol moiety can be cyclic, straight, orbranched, and saturated or unsaturated. Some examples of ethoxylatedfatty alcohols include ethylene glycol ethers of oleth alcohol, stearethalcohol, lauryl alcohol and isocetyl alcohol. Poloxamers are ethyleneoxide and propylene oxide block copolymers, having from about 15 toabout 100 moles of ethylene oxide. Alkyl polysaccharide (“APS”)surfactants (for example, alkyl polyglycosides) contain a hydrophobicgroup with about 6 to about 30 carbons and a polysaccharide (forexample, polyglycoside) as the hydrophilic group. An example ofcommercial nonionic surfactant is FOA-5 (Octel Starreon LLC., Littleton,Colo.).

Specific examples of suitable nonionic surfactants include alkanolamidessuch as cocamide diethanolamide (“DEA”), cocamide monoethanolamide(“MEA”), cocamide monoisopropanolamide (“MIPA”), PEG-5 cocamide MEA,lauramide DEA, and lauramide MEA; alkyl amine oxides such as lauramineoxide, cocamine oxide, cocamidopropylamine oxide, andlauramidopropylamine oxide; sorbitan laurate, sorbitan distearate, fattyacids or fatty acid esters such as lauric acid, isostearic acid, andPEG-150 distearate; fatty alcohols or ethoxylated fatty alcohols such aslauryl alcohol, alkylpolyglucosides such as decyl glucoside, laurylglucoside, and coco glucoside.

A surfactant used in preparation of the present materials can bezwitterionic, having both a formal positive and negative charge on thesame molecule. The positive charge group can be quaternary ammonium,phosphonium, or sulfonium, whereas the negative charge group can becarboxylate, sulfonate, sulfate, phosphate or phosphonate. Similar toother classes of surfactants, the hydrophobic moiety can contain one ormore long, straight, cyclic, or branched, aliphatic chains of about 8 to18 carbon atoms. Specific examples of zwitterionic surfactants includealkyl betaines such as cocodimethyl carboxymethyl betaine, lauryldimethyl carboxymethyl betaine, lauryl dimethyl alpha-carboxyethylbetaine, cetyl dimethyl carboxymethyl betaine, laurylbis-(2-hydroxyethyl)carboxy methyl betaine, stearylbis-(2-hydroxypropyl)carboxymethyl betaine, oleyl dimethylgamma-carboxypropyl betaine, and laurylbis-(2-hydroxypropyl)alphacarboxy-ethyl betaine, amidopropyl betaines;and alkyl sultaines such as cocodimethyl sulfopropyl betaine,stearyidimethyl sulfopropyl betaine, lauryl dimethyl sulfoethyl betaine,lauryl bis-(2-hydroxyethyl)sulfopropyl betaine, andalkylamidopropylhydroxy sultaines.

A surfactant used in preparation of the present materials can beamphoteric. Examples of suitable amphoteric surfactants include ammoniumor substituted ammonium salts of alkyl amphocarboxy glycinates and alkylamphocarboxypropionates, alkyl amphodipropionates, alkylamphodiacetates, alkyl amphoglycinates, and alkyl amphopropionates, aswell as alkyl iminopropionates, alkyl iminodipropionates, and alkylamphopropylsulfonates. Specific examples are cocoamphoacetate,cocoamphopropionate, cocoamphodiacetate, lauroamphoacetate,lauroamphodiacetate, lauroamphodipropionate, lauroamphodiacetate,cocoamphopropyl sulfonate, caproamphodiacetate, caproamphoacetate,caproamphodipropionate, and stearoamphoacetate.

A surfactant used in preparation of the present materials can also be apolymer such as N-substituted polyisobutenyl succinimides andsuccinates, alkyl methacrylate vinyl pyrrolidinone copolymers, alkylmethacrylate-dialkylaminoethyl methacrylate copolymers,alkylmethacrylate polyethylene glycol methacrylate copolymers,polystearamides, and polyethylenimine.

A surfactant used in preparation of the present materials can also be apolysorbate type nonionic surfactant such as polyoxyethylene (20)sorbitan monolaurate (Polysorbate 20), polyoxyethylene (20) sorbitanmonopalmitate (Polysorbate 40), polyoxyethylene (20) sorbitanmonostearate (Polysorbate 60) or polyoxyethylene (20) sorbitanmonooleate (Polysorbate 80).

A surfactant used in preparation of the present materials can be anoil-based dispersant, which includes alkylsuccinimide, succinate esters,high molecular weight amines, and Mannich base and phosphoric acidderivatives. Some specific examples are polyisobutenylsuccinimide-polyethylenepolyamine, polyisobutenyl succinic ester,polyisobutenyl hydroxybenzyl-polyethylenepolyamine, andbis-hydroxypropyl phosphorate.

The surfactant used in preparation of the present materials can be acombination of two or more surfactants of the same or different typesselected from the group consisting of anionic, cationic, nonionic,zwitterionic, amphoteric and ampholytic surfactants. Suitable examplesof a combination of two or more surfactants of the same type include,but are not limited to, a mixture of two anionic surfactants, a mixtureof three anionic surfactants, a mixture of four anionic surfactants, amixture of two cationic surfactants, a mixture of three cationicsurfactants, a mixture of four cationic surfactants, a mixture of twononionic surfactants, a mixture of three nonionic surfactants, a mixtureof four nonionic surfactants, a mixture of two zwitterionic surfactants,a mixture of three zwitterionic surfactants, a mixture of fourzwitterionic surfactants, a mixture of two amphoteric surfactants, amixture of three amphoteric surfactants, a mixture of four amphotericsurfactants, a mixture of two ampholytic surfactants, a mixture of threeampholytic surfactants, and a mixture of four ampholytic surfactants.

Thin Polymeric Layer Materials

The techniques described above include the use of polymers to form asurface treatment 201 on high aspect ratio carbon nanotubes in order topromote adhesion with the active material particles 300. While severaladvantageously suitable polymers have been described, it is to beunderstood that other polymer material may be used, including thefollowing.

The polymer used in preparation of the present materials can be polymermaterial such a water processable polymer material. In variousembodiments any of the follow polymers (and combinations thereof) may beused: polyacrilic acid (PAA), poly(vinyl alcohol) (PVA), poly(vinylacetate) (PVAc), polyacrylonitrile (PAN), polyisoprene (Plpr),polyaniline (PANi), polyethylene (PE), polyimide (PI), polystyrene (PS),polyurethane (PU), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP).In some embodiments. Another exemplary polymer material is fluorineacrylic hybrid Latex (TRD202A), and is supplied by JSR Corporation.

EXAMPLES

The following non-limiting examples further describe the application ofthe teachings of this disclosure. In the following examples, the term“binder free” or “binderless” electrodes reference to electrodes of thetype described in detail above featuring a 3D matrix or scaffold of highaspect ratio carbons which a surface treatment thereon which promotesadhesion of active material to the scaffold without the need for bulkpolymeric binders such as PVDF.

As used in the following the term C-rate refers to a measure of the rateat which a battery is discharged relative to its maximum capacity. A 1Crate means that the discharge current will discharge the entire batteryin 1 hour. For a battery with a capacity of 100 Amp-hrs, this equates toa discharge current of 100 Amps.

Example 1—Electric Vehicle Battery Cell

The following battery cell suitable for use in Electric Vehicles (“EV”).This cell combines cathode and anode technology of the type describedherein for use, e.g., in an EV application. Key high-level benefitsinclude lower cost to manufacture, higher energy density, excellentpower density, and wide temperature range operation. These benefits arederived from the herein described approach to manufacturing batteryelectrodes, which eliminates the use of PVDF polymer binders and toxicsolvents like N-Methyl-2-pyrrolidone (NMP). The result is a substantialperformance advantage in range, charging speed, and acceleration for theend-user with a manufacturing process that is lower cost, less capitalintensive and safer for the battery producers.

The teachings herein provide a technology platform to manufactureelectrodes for energy storage which may exhibit the followingadvantages: reduction in cost of manufacturing and in the $/kWh ofresulting LIBs, increase in energy density by combining cathodes withthick coatings and high capacity anodes featuring high performanceactive materials such as Si or SiOx, fast charging. The teachings hereinprovide a scalable technology to improve power density in energystorage, by removing conventional polymer binders from the activematerial coatings.

Conventional electrodes for LiBs are fabricated by mixing an activematerial, conductive additives and a polymer binder in a slurry.Conventional cathodes are manufactured using NMP-based slurries and PVDFpolymer binders. Those binders have very high molecular weight andpromote cohesion of active material particles and adhesion to thecurrent collector foil via two main mechanisms: 1) the entanglementpromoted by long polymer chains, and 2) hydrogen bonds between thepolymer, the active material, and the current collector. However, thepolymer binder-based method presents significant drawbacks inperformance: power density, energy density, and also cost tomanufacture.

The teachings herein provide electrodes that do not have PVDF binders incathodes, or other conventional binders in anodes. Instead, as detailedabove a 3D carbon scaffold or matrix holds active material particlestogether to form a cohesive layer that is also strongly attached to themetallic current collector. Such active material structure is createdduring slurry preparation and subsequently in a roll to roll (“R2R”)coating and drying process. One of the main advantages of thistechnology is its scalability and “drop-in” nature since it compatiblewith conventional electrode manufacturing processes.

The 3D carbon matrix is formed during a slurry preparation using thetechniques described herein: high aspect ratio carbon materials areproperly dispersed and chemically functionalized using, e.g., a 2-stepslurry preparation process (such as the type described above withreference to FIG. 6 ). The chemical functionalization is designed toform an organized self-assembled structure with the surface of activematerial particles, e.g. NMC particles for use in a cathode or siliconparticles (“Si”) or Silicon Oxide (“SiOx”) particles in the case of ananode. The so formed slurry may be based on alcohol solvents forcathodes and water for anodes, and such solvents are very easilyevaporated and handled during the manufacturing process. Electrostaticinteractions promote the self-organized structure in the slurry, andafter the drying process the bonding between the so formed carbon matrixwith active material particles and the surface of the current collectoris promoted by the surface treatment (e.g., functional groups on thematrix) as well as the strong entanglement of the active material in thecarbon matrix.

As will be understood by one skilled in the art, the mechanicalproperties of the electrodes can be readily modified depending on theapplication, and the mass loading requirements by tuning the surfacefunctionalization vs. entanglement effect.

After coating and drying, the electrodes undergo a calendaring step tocontrol the density and porosity of the active material. In NMC cathodeelectrodes, densities of 3.5 g/cc or more and 20% porosity or more canbe achieved. Depending on mass loading and LIB cell requirements theporosity can be optimized. As for SiOx/Si anodes, the porosity isspecifically controlled to accommodate active material expansion duringthe lithiation process.

In some typical applications, the teachings herein may provide areduction in $/kWh of up to 20%. By using friendly solvents that areeasily evaporated, the electrode throughput is higher, and moreimportantly, the energy consumption from the long driers issignificantly reduced. The conventional NMP recovery systems are alsomuch simplified when alcohol or other solvent mixtures are used.

The teachings herein provide a 3D matrix that dramatically boostselectrode conductivity by a factor of 10× to 100× compared to electrodesusing conventional binders such as PVDF, which enables fast charging ata battery level. Thick electrode coatings in cathode up to 150 um perside (or more) of current collector are possible with this technology.The solvents used in the slurry in combination with a strong 3D carbonmatrix are designed to achieve thick wet coatings without crackingduring the drying step. Thick cathodes with high capacity anodes arewhat enable a substantial jump in energy density reaching 400 Wh/kg ormore.

Fast charging is achieved by combining high capacity anodes that arelithiated through an alloying process (Si/SiOx) and by reducing theoverall impedance of the cell when combining anodes and cathodes asdescribed herein. The teachings herein provide fast charging by havinghighly conductive electrodes, and in particular highly conductivecathode electrodes.

One exemplary embodiments includes a Li-ion battery energy storagedevices in a pouch cell format that combines Ni-rich NMC active materialin the cathodes and SiOx and graphite blend active material in theanodes, where both anodes and cathodes are made using a 3D carbon matrixprocess as described herein.

A schematic of the electrode arrangement pouch cell devices is shown inFIG. 7 . As shown, a double-sided cathode using polymer binder freecathode layers on opposing sides of an aluminum foil current collectorare disposed between two single sided anodes each having a polymerbinder free anode layer disposed on a copper foil current collector. Theelectrodes are be separated by permeable separator material (not shown)wetted with electrolyte (not shown). The arrangement can be housed in apouch cell of the type well known in the art.

These devices may feature high mass loading of Ni-rich NMC cathodeelectrodes and their manufacturing method: mass loading=20-30 mg/cm²,specific capacity >210 mAh/g. SiOx/Graphite anode (SiOx content=˜20 wt.%) based electrodes and their material synthesis and manufacturingmethod: mass loading 8-14 mg/cm², reversible specific capacity ≥550mAh/g. Long life performance specially for SiOx/Graphite anode basedLi-ion based electrolyte for battery: from −30 to 60° C. High-energy,high-power density, and long cycle life Ni-rich NMCcathode/SiOx+Graphite/Carbon+based Li-ion battery pouch cells: capacity≥5 Ah, Specific Energy ≥300 Wh/kg, Energy Density ≥800 Wh/L, with acycle life of more than 500 cycles under 1C-Rate charge-discharge, andultra-high-power fast charge-discharge C-Rate (Up to 5C-Rate)capabilities. A summary of performance parameters for a pouch cell ofthis type are summarized in FIG. 8 .

Example 2 Comparative Performance NMC811 Lithium Ion Battery

As detailed above, the teachings herein provide electrodes configuredwith an advanced 3-D high aspect ratio carbon binding structure thateliminates the need for polymer binders, providing greater power, energydensity (e.g., via thicker electrodes and higher mass loading of activematerial), and performance in extreme environments compared totraditional battery electrode designs. The high-performance Li-ionbattery energy storage devices are designed and manufactured with anoptimized capacity ratio design of binder-free cathode/anode electrodes,anode electrode pre-lithiation, and wide operating temperatureelectrolyte (e.g., −30 to 60° C.), and optimized test formationprocesses.

As described herein, the electrodes are manufactured by completelyremoving high molecular weight polymers such as PVDF and the toxic NMPsolvent from the active material layer. This dramatically improves LiBperformance while decreasing the cost of manufacturing and the capitalexpenditures related to mixing, coating and drying, NMP solventrecovery, and calendaring. In embodiments of the electrodes, a 3Dnanoscopic carbon matrix works as a mechanical scaffold for theelectrode active material and mimics the polymer chain entanglement.Chemical bonds are also present between the surface of the carbon, theactive materials, and the current collector promoting adhesion andcohesion. As opposed to polymers, however, the 3D nanoscopic carbonmatrix is very electrically conductive, which enables very high power(high C-rates). This scaffold structure is also more suitable forproducing thick electrode active material, which is a powerful way toincrease the energy density of LiB cells.

In the present example, a binder free cathode was produced according tothe teachings of this disclosure featuring a NMC811 as an activematerial and incorporated in a Li-ion battery (LIB). The cell featured agraphite anode of the conventional type known in the art. The cell wasconstructed as described above with reference to FIG. 7 using theparameters summarized in FIG. 9 . A conventional electrolyte was usedcomposed of 1M of LiPF6 in an solvent mixture of ethylene carbonate anddimethyl carbonate with 1% by weight vinyl carbonate additive. As acomparison, an otherwise identical cell was produced using a PVDF binderbased cathode. The performance of the cells was compared as describedbelow, showing clear advantages for the binder free cathode cell.

As shown in the results summarized in FIG. 10 , the binder free cell canreach a specific energy as high as 320 Wh/kg based on 20 Ah battery celldesign and a graphite anode with more than 2,000 cycle cycle life under2C-rate charge/discharge. In comparison, the conventional binder-basedcathode cell can only achieve 100-250 Wh/kg in specific energy at thecell level.

The binder free cathode cell exhibits ultra-high-power fastcharge-discharge C-Rate, up to 5C-Rate with >50% capacity retention.FIG. 10 shows a comparison of the charge-discharge curves at variousC-rates for the binder free cathode cell (left) and the conventionalbinder-based cathode cell (right). The binder free cathode cellcharge-discharge curve shows over 60% capacity retention of a combinedcharge-discharge at a 5C rate. Accordingly, separate discharge or chargewould exhibit even higher capacity retention. Note in the exampleprovided a conventional graphite anode is used, initial experimentalresults show that when a Si-dominant anode is combined with NMC811cathode used in the present example, 10C charge rate is achievable.

FIG. 11 shows a comparison of the cycle life of the above describedcells. The cells were repetitively cycled between voltages of 2.75V and4.2V at 25° C., and the discharge capacity recorded. The binder freecathode cell exhibits a lifetime of greater than 2,000 cycles withdischarge capacity loss of less than 20%. In contrast the binder-basedcathode cell experiences greater than 20% discharge capacity loss afteronly about 1,000 cycles.

Example 3—Pouch Half Cell Comparison

Binder free cathode electrodes of the type described herein canadvantageously achieve high mass loadings for example, a mass loading of45 mg/cm² per side of NMC811 active material is possible. The presentexample sets forth experimental results showing the performance of sucha high mass loading binder free electrode in comparison with a controlelectrode featuring PVDF binder and an NMC811 active material.

To perform the comparison, half-cells of the type shown in FIG. 12 wereconstructed using a one sided cathode (either binder free or the binderbased control) and a lithium foil on copper substrate as the counterelectrode for the cell. The half cells underwent charge rate testingunder various current densities and the results summarized below.

FIG. 13 is a plot showing potential (referenced to the Li/Li+ potential)vs specific capacity for binder free cathode half cell (solid traces)and reference binder based cathode half cell (dashed traces) at variouscurrent densities. At all current densities (and thus all C-rates), thebinder free cathode half cells show better performance (as indicated bythe relative rightward shift of the trace).

FIG. 14 is a plot showing potential (referenced to the Li/Li+ potential)vs volumetric capacity for binder free cathode have cell (solid traces)and reference binder based cathode half cell (dashed traces) at variouscurrent densities. At all current densities (and thus all C-rates), thebinder free cathode half cells show better performance (as indicated bythe relative rightward shift of the trace).

FIG. 15 shows a plot of volumetric capacity vs current density forbinder free cathode half cells (upper trace) and reference binder basedcathode half cell (lower trace). At all current densities (and thus allC-rates), the binder free cathode half cells show better performance,with the relative performance gap widening at higher C-rates.

FIG. 16 shows a Nyquist plot resulting from electrochemical impedancespectroscopy for several binder free cathode half cells (square, circleand triangle labeled traces) and a reference binder based cathode halfcells. The binder free cathode half cells exhibit significantly betterperformance than the reference cell.

It can be seen from the FIG.s that when the current density increasesfrom 0.5 to 10 mA/cm² (1.2 C-Rate), the discharge capacity retention forbinder-free NMC811 electrode has a much higher value compared with abinder based PVDF control NMC811 electrode, even though both electrodeshave the same mass loading of 45 mg/cm². Note that this C-Rate testunder various current densities is presented as a relative comparisonbetween conventional binder based PVDF cathodes and binder freecathodes, and does not reflect the absolute C-rate performance in a fullcell configuration, e.g., as presented in the Examples 1 and 2 above.

CONCLUSION

In summary, disclosed herein is an energy storage cell comprising afirst electrode; a second electrode; a permeable separator disposedbetween the first electrode and the second electrode; and an electrolytewetting the first and second electrodes; wherein the first electrodecomprises a network of elements defining void spaces within the network;and active material comprising lithium metal oxide disposed in the voidspaces within the network and enmeshed in the network; wherein theelectrode active layer contains less than 0.1% percent by weight ofpolymeric binders disposed in the void spaces; wherein the active layeris greater than 99% by weight active material; wherein the energystorage cells has an operational voltage in the range of 1.0 V to 5.0 V,a gravimetric energy density of at least 300 Watt-hour per kilogram(Wh/Kg), a volumetric energy density of at least 800 Watt-hour per liter(Wh/L), a cycle life of at least 1,000 charge discharge cycles.

In an embodiment, the electrode active layer contains less than 0.1%percent by weight of polyvinylidene fluoride. In another embodiment, thefirst electrode comprises a cathode with density of at least of 3.5 g/ccand porosity of at least 20 volume percent, based on a total volume ofthe cathode active layer. In yet another embodiment, at least the firstelectrode is a double sided electrode with active layer thickness of atleast 150 micrometer per side. In another embodiment, at least twoelectrodes are double sided electrodes with active layer thickness of atleast 150 micrometer per side.

Any terms of orientation provided herein are merely for purposes ofintroduction and are not limiting of the invention. For example, a “top”layer may also be referred to as a second layer, the “bottom” layer mayalso be referred to as a first layer. Other nomenclature andarrangements may be used without limitation of the teachings herein.

Various other components may be included and called upon for providingfor aspects of the teachings herein. For example, additional materials,combinations of materials and/or omission of materials may be used toprovide for added embodiments that are within the scope of the teachingsherein.

A variety of modifications of the teachings herein may be realized.Generally, modifications may be designed according to the needs of auser, designer, manufacturer or other similarly interested party. Themodifications may be intended to meet a particular standard ofperformance considered important by that party. Similarly, acceptabilityof performance is to be assessed by the appropriate user, designer,manufacturer or other similarly interested party.

While some chemicals may be listed herein as providing a certainfunction, a given chemical may be useful for another purpose.

When introducing elements of the present invention or the embodiment(s)thereof, the articles “a,” “an,” and “the” are intended to mean thatthere are one or more of the elements. Similarly, the adjective“another,” when used to introduce an element, is intended to mean one ormore elements. The terms “including” and “having” are intended to beinclusive such that there may be additional elements other than thelisted elements. As used herein, the term “exemplary” is not intended toimply a superlative example. Rather, “exemplary” refers to an embodimentthat is one of many possible embodiments.

The entire contents of each of the publications and patent applicationsmentioned above are incorporate herein by reference. In the event thatthe any of the cited documents conflicts with the present disclosure,the present disclosure shall control.

Note that it is not intended that any functional language used in claimsappended herein be construed as invoking 35 U.S.C. § 112(f)interpretations as “means-plus-function” language unless specificallyexpressed as such by use of the words “means for” or “steps for” withinthe respective claim.

While the invention has been described with reference to exemplaryembodiments, it will be understood that various changes may be made andequivalents may be substituted for elements thereof without departingfrom the scope of the invention. For example, in some embodiments, oneof the foregoing layers may include a plurality of layers there within.In addition, many modifications will be appreciated to adapt aparticular instrument, situation or material to the teachings of theinvention without departing from the essential scope thereof. Therefore,it is intended that the invention not be limited to the particularembodiment disclosed as the best mode contemplated for carrying out thisinvention, but that the invention will include all embodiments fallingwithin the scope of the appended claims.

What is claimed is:
 1. An energy storage cell comprising a firstelectrode; a second electrode; a permeable separator disposed betweenthe first electrode and the second electrode; and an electrolyte wettingthe first and second electrodes; wherein the first electrode contains anelectrode active layer that comprises: a network of elements definingvoid spaces within the network; and active material comprising lithiummetal oxide disposed in the void spaces within the network and enmeshedin the network; wherein the electrode active layer contains less than0.1% percent by weight of polymeric binders disposed in the void spaces;wherein the electrode active layer comprises greater than 99% by weightof the active material; wherein the energy storage cells has anoperational voltage in the range of 1.0 V to 5.0 V, a gravimetric energydensity of at least 300 Wh/Kg, a volumetric energy density of at least800 Wh/L, a cycle life of at least 1,000 charge discharge cycles.
 2. Theenergy storage cell of claim 1, wherein the electrode active layercontains less than 0.1% percent by weight of polyvinylidene fluoride. 3.The energy storage cell of claim 1, wherein the first electrodecomprises a cathode with density of at least of 3.5 g/cc and porosity ofat least 20 volume percent, based on a total volume of the cathodeactive layer.
 4. The energy storage cell of claim 3, wherein the firstelectrode is a double sided electrode with active layer thickness of atleast 150 micrometer per side.
 5. The energy storage cell of claim 1,wherein the network of elements include high aspect ratio carbonelements that each have two major dimensions and one minor dimension,wherein the ratio of the length of each of the major dimensions is atleast 10 times that of the minor dimension.
 6. The energy storage cellof claim 5, wherein the high aspect ratio carbon elements compriseelements each have one major dimension and two minor dimension, whereinthe ratio of the length of each the major dimension is at least 10 timesthat of each of the minor dimensions.
 7. The energy storage cell ofclaim 5, wherein the high aspect ratio carbon elements comprise carbonnanotubes or carbon nanotube bundles.
 8. The energy storage cell ofclaim 5, wherein the high aspect ratio carbon elements comprise grapheneflakes.
 9. The energy storage cell of claim 1, wherein the electrodeactive layer contains less than 10% by weight polymeric binders disposedin the void spaces
 10. The energy storage cell of claim 1, wherein theelectrode active layer contains less than 1% by weight polymeric bindersdisposed in the void spaces.
 11. The energy storage cell of claim 1,wherein the electrode active layer is substantially free of polymericmaterial other than a surface treatment.
 12. The energy storage cell ofclaim 1, wherein the electrode active layer is substantially free ofpolymeric material.